1. Field of the Invention
This invention relates to communication or electrical connectors featuring capacitive compensation to suppress or to compensate for crosstalk.
2. Discussion of the Known Art
There is a need for a durable, high-frequency communication connector that suppresses or compensates for crosstalk produced among different signal paths within the connector. As defined herein, crosstalk results when signals conducted over a first path, e.g., a pair of terminal contact wires associated with a communication connector, are partly transferred by electromagnetic coupling into a second path, e.g., another pair of terminal contact wires in the same connector. The transferred signals define "crosstalk" in the second signal path, and this crosstalk degrades any signals that are being routed over the second path.
For example, an industry type RJ-45 communication connector typically includes four pairs of terminal wires defining four different signal paths. In the conventional RJ-45 plug and jack connectors, all four pairs of terminal wires extend closely parallel to one another over the length of the connectors. Thus, crosstalk is induced among different pairs of terminal wires, particularly in mated plug and jack combinations, and the amplitude of the crosstalk increases as the coupled signal frequencies or data rates increase.
Applicable industry standards for rating crosstalk performance of communication connectors, do so in terms of near-end crosstalk or "NEXT". Further, NEXT ratings are typically specified for mated plug and jack combinations, wherein the input terminals of the plug connector are used as a reference plane. Communication links using unshielded twisted pairs (UTP) of copper wire are now expected to support data rates up to not only 100 MHz or industry standard "Category 5" performance, but to meet proposed "Category 6" levels which call for at least 46 dB crosstalk loss at 250 MHz.
Crosstalk compensation circuitry may be provided on or within layers of a printed wire board, to which spring terminal contact wires of a communication jack are connected within a jack housing. See U.S. patent application No. 08/923,741 filed Sep. 29, 1997, now U.S. Pat. No. 5,997,358, and assigned to the assignee of the present application and invention. All relevant portions of the '741 application are incorporated by reference herein. See also U.S. Pat. No. 5,299,956 (Apr. 5, 1994).
U.S. patent application No. 09/327,882 filed Jun. 8, 1999, and assigned to the assignee of the present application and invention, discloses an enhanced communication connector assembly with crosstalk compensation. A number of terminal contact wires have base portions supported on a wire board, with free end portions opposite the base portions for making electrical contact with a mating connector. A crosstalk compensating device is provided on the wire board, wherein the device is arranged to cooperate with sections of selected terminal contact wires to provide capacitive coupling between the selected contact wires. U.S. patent application No. 09/344,831 filed Jun. 25, 1999, and also assigned to the present assignee, relates to an assembly for capacitive crosstalk compensation in a communication connector, wherein electrodes of housed compensation capacitors are arranged to contact selected terminal contact wires inside a communication connector so as to provide capacitive coupling between the selected wires. All relevant portions of the mentioned '882 and '831 applications are incorporated by reference.
U.S. Pat. No. 5,547,405 (Aug. 20, 1996) relates to a crosstalk suppressing connector having first and second signal carrying pairs of elongated, laterally spaced contacts mounted in a housing. An intermediate portion of one contact of one pair is formed to overlie an intermediate portion of another contact of the other pair, with a dielectric between the overlying portions. The overlying portions of the contacts are formed relatively close to insulation displacement connector terminals provided at one end of the contacts, and remote from the tail ends of the contacts where connections with a mating plug connector are established.
While capacitive crosstalk suppression or compensation is desirable since it can be applied or injected over a relatively short length of contact wires within a connector, the point at which such compensation is introduced ideally should be as close as possible to the source of the offending crosstalk, e.g., a mating plug.